This 3D-Printed Microturbine Engine Is Designed To Do More Than Fly

One aspect of how industrial 3D printing works that is hard to grasp at first, is its ability to build parts inside of other parts. A metal 3D printer makes an object one hair-thin horizontal layer at a time. So imagine 3D printing an item like a chain. It’s constructed already linked in completely solid circles. By contrast, in traditional manufacturing, individual links are first straight, then bent, and joined together one at a time, which is slower, more labor intensive, and has weak points at each link. It’s the same age-old manufacturing principle for jewelry as it is for chains holding the anchors of navy ships.

3D printing’s ability to fabricate objects, like an already linked chain, is disrupting the way things have always been manufactured. It offers engineers new design freedom, unconstrained from the limitations of traditional manufacturing.

To drive this point home, using a far more complex 3D printed part than a chain link, software company PTC displayed a fully 3D-printed — in one piece — jet engine at its company product launch event last month in Boston, Mass.

The Engine Assembly Born Fully Assembled

The microturbine engine weighs about eight pounds and is 3D printed as a single component, including all rotating and stationary parts, all at once. Although it looks solid from the outside, inside are lattice structures to minimize weight and channels to enable air and fuel flow. A typical microturbine, by contrast, contains upwards of 33 parts that are individually machined and then assembled.

“There really are no other components required for this engine to function other than the housing,” says Steve Dertien, PTC’s chief technology officer. “Everything else, from the bearings to the seal to the cooling, is designed-in.”

PTC says this additively printed engine would fire up like any other microturbine engine, although it hasn’t actually been tested in this way. As a non-commercial research project, PTC does not plan to sell this particular engine, but there is no shortage of companies looking to make compact turbines more affordable for applications, such as lighter, moderate-sized UAVs.

“Today, microturbine engines require complex assembly processes of many expensive parts, which puts customers directly in the crosshairs of supply chain dependencies, limited availability, and their manufacturers maintaining the right employee expertise to complete assemblies,” PTC said at the product’s launch.

A monolithic, 3D-printed microturbine engine can dramatically bring down costs, speed up production, and introduce new efficiencies not possible with traditionally manufactured engines.

With 3D printing, also called additive manufacturing, there’s no tooling required for molding or machining parts. It eliminates the need to weld or join parts which can introduce weaknesses. And there’s also the possibility of on-demand manufacturing on-site since there’s no need to ship any components from elsewhere or have skilled labor on hand.

“When the engine is just one unit, it’s cheap to produce and to replace,” says Dertien, “You don’t have to think about replacement parts. If it breaks, print a new one.”

The engine took 13 hours to print on a metal laser powder bed fusion 3D printer from EOS (its M300 model) using Inconel as the material. Inconel is an extremely strong and heat-resistant metal that’s very difficult to machine so, in traditional manufacturing, it’s often only used for the exhaust parts of a turbine engine.

This particular microturbine engine is meant to be an iconic part that demonstrates the possible, says Dertien. “The Uber goal was to do something that’s extraordinary, but accessible.”

Of course, PTC is not a metal additive manufacturer. It makes software.

The engine project was a partnership with researchers at Technion – Israel Institute of Technology. If they could develop and 3D print a workable jet engine — one of the most complex pieces of machinery there is, considering the performance requirements for operation and the intricacy of the components — it would demonstrate how engineers can rethink manufacturing these kinds of engines using advanced software that understands additive manufacturing.

“The additively printed engine is a culmination of the last five to six years of putting additive engineering tools into CAD (computer-aided design) software,” says Dertien. “It represents the cutting edge of what additive manufacturing is capable of, and some of these features would be unthinkable just a few years ago.”

Creo is the name of PTC’s design and engineering software platform with tools specifically to incorporate the types of designs and part features that are only possible with additive manufacturing. Yet, these tools are often a mystery to engineers using the software for their day-to-day work.

Metal additive manufacturing is only a few decades old, notes Dertien, so engineers may not have learned about it in school, plus a lot has changed. Engineering software like Creo can calculate the wall thickness the turbine should have to meet the anticipated pressure, it can generate the ideal lattice structure for the internal walls, and it can take into account that the part will be 3D printed, so it may offer ideas for consolidating parts.

In many ways, engineering design software has been ahead of the curve in additive manufacturing. The ability to design parts specifically for additive manufacturing is here, but the application of it is a bit lagging, apart from rocket engines, medical implants, and concept projects, such as the Czinger 21C Hypercar.

Creo is one of a breed of CAD and engineering software programs, including Autodesk’s Fusion 360, Siemens NX, nTop, and Dassault Systèmes’ CATIA, hoping to spur more adoption of additive manufacturing by providing the design tools that make it possible.

PTC wants engineers to “think additively” and apply the attributes of the technology to engines, satellites, cars, and countless other complex assemblies.

Creo, and other software platforms like it, today include complex algorithms to optimize a product’s designs based on its size and weight constraints. Products can begin as specifications of what it has to achieve, instead of the constraints of how it needs to be built. The collection of processes and tools to design a part to be 3D printing is called DfAM, design for additive manufacturing.

When it came to designing the jet engine assembly, PTC engineers, led by Dr. Ronen Ben Horin, a VP of technology at PTC and a senior research fellow at Technion, and Beni Cukurel, an associate professor of aerospace at Technion, used Creo to not only design but simulate the engine’s performance. The project took about two years and is ongoing. The next iteration of the microturbine will streamline manufacturing even more, according to Dertien.

Other manufacturers, including California-based Sierra Turbines, are also in pursuit of the monolithic 3D-printed economical and efficient microturbine enabled by DfAM software tools.

Competition for better engines, machines, and robotics that aren’t constrained by the way things have always been made continues to drive adoption of additive manufacturing.